Vacuum switch

ABSTRACT

Circumferential current flow which serves to draw contact members together in a vacuum is produced by a vacuum switch having cup-shaped switch contacts having ring-shaped side portions which are subdivided by slots into segments. The circumferential direction of the current is produced by circumferential slots in the side portions which slots consist of a gap which extends parallel through the contact surface and connects with a vertical, chordially aligned cut in the contact surface.

[ VACUUM SWlTGllll [75] Inventor: Hans Bettge, Berlin, Germany [73]Assignee: Siemens Alttiengesellschait, Berlin and Munich, Germany 221Filed: .lan.l1tl,1972 21 App1.No.:2l16,523

[30] Foreign Application Priority Data [in 3,823,287 [451 Jul 9,1974

3,622,724 11/1971 Sofianek ..200/144B Primary Examiner-Robert S. MaconAttorney, Agent, or Firm-Hill, Gross, Simpson, Van Santen, Steadman,Chiara & Simpson Circumferential current flow which serves to drawcontact members together in a vacuum is produced by a vacuum switchhaving cup-shaped switch contacts having ring-shaped side portions whichare subdivided by slots 'into segments. The circumferential direction ofthe current is produced by circumferential slots in the side portionswhich slots consist of a gap which extends parallel through the contactsurface and connects with a vertical, chordially aligned cut in thecontact surface.

5 Claims, 4 Drawing Figures Apr. 1, 1971 Germany 2015528 [52] US. G12011/1144 B [51] llnt. 1C1. Hillllli 33/66 [58] Field oi Search 200/144B, 166 B [56] References Cited UNlTED STATES PATENTS 3,225,16712/1965 Greenwood... ZOO/144B FATENTEDJUL W V weaves? QQ R WNI L 1VACUUM swrrcn BACKGROUND OF THE INVENTION This invention generallyrelates to an electric switch and more particularly concerns a vacuumswitch wherein two contacts relatively movable toward and away from eachother have opposed planar contact surfaces facing each other wherein atleast one of the contact surfaces takes the form of a ring-shaped bridgewhich is subdivided into segments by slot means to force the currentwhich flows between the opposed contacts into a path which path has acomponent extending in the circumferential direction of the ringshapedbridge means.

It is known in the prior art as shown, for example, in the GermanLetters Patent 1,196,751 to have ringshape bridges of the contact piecesdivided into segments, however, the slots which define the segments areinclined with respect to the axis of the bridge. As a result, the priorart contact arrangements have a noticeable component of the currentextending in the direction of the axis of the opposed contacts.

It is also known from the German Letters Patent 1,236,053 to provide theparticular segments with a slot extending between points of the endsurfaces of the segment which slots are staggered with respect to eachother about the ring-shaped bridges in order to force the current toflow in a path with a component in the circumferential direction of thering-shaped bridges. In this prior art embodiment, however, a relativelylarge axially directed current component is sought to be avoided byproviding a projection on the contacting surface of the contactingpieces so that the arcing across the contacts is caused to occur at aspecified place. Thus, according to this prior art construction eventhough the current flowing through the contacts will have acircumferentially directed portion, the concentration of the arcingacross the projections will have the effect of deteriorating theelectrical properties of the vacuum switch.

SUMMARY'OF THE INVENTION The disadvantages of the prior art are overcomeby the vacuum switch means according to the invention herein'comprisinga pair of generally axially aligned opposedcontacts, 'at least one ofwhich contacts has a ring-shaped bridge means that is subdivided intosegments by generally circumferentially extending slot means whereby thecurrent flowing through the switching contacts follows a path as closeas possible to the contacting surfaces and is directed practicallyexclusively in a direction tangential to the'axis of the switchingcontacts. This current path produces a magnetic field under theinfluence of which a light are occurring between the opposed contactsurfaces is moved around the ring-shaped contact surface. By this meansand by means of chordally aligned slots in the contact surface areignition of the lighting ark and damage to the contact surfaces isavoided.

The slot means has a first and second portion with the first portion ofthe slot means lying in a plane generally parallel to the contactsurfaces and the second portion of the slot means extending between thefirst portion and the contact surfaces. The second portion of the slotmay be generally perpendicularly inclined to the contact surface and maybe positioned to lie on a chord 2. of the ring-shaped bridge means. Whenboth of the opposed contacts have the ring-shaped bridge means thereonthe first portions of the slot means on each of the contacts may bearranged to extend in opposite directions from their respective secondportions whereby the magnetic fields produced by each will be attractiveto each other. By means of the structural features hereabove set forththe current flowing through the contacts is almost entirely free ofaxial components near the contact surface and flows in a distinctlycircumferential direction about the ring-shaped bridge means to producea magnetic field which forces a light are occurring between the contactsurfaces to move around the contact surfaces. The chordally arrangedvertical cuts forming the second portion of the slot means facilitatethe passage of the light arcs over the vertical cuts in the contactsurface so that the light arc may move freely around the ring-shapebridges.

In order to obtain the desired current loop with the distinct tangentialdirection of the current in each contact, the contact pieces areadvantageously designed symmetrically and arranged in' the vacuum switchstaggered in relationship to each other circumferentially by aboutone-half the length of the segments. I

In order to increase the mechanical rigidity of the switching contactsthe first portions of the slot adjacent the second portions may besupported by bridging members consisting of a material which has a lowerelectric conductivity than the material of the contacts. Advantageouslywe have found that where the bridging member comprises a screw means itis easily adjustable to maintain the slot means at a predeterminedwidth.

BRIEF DESCRIPTION OF THE DRAWINGS Other objects, features and advantagesof the invention will be readily apparent from the following descriptionof certain preferred embodiments thereof, taken inconjunction with theaccompanying drawings, although variations and modifications may beeffected without departing from the spirit and scope of the novelconcepts of the disclosure and in which:

FlG. 1 is a schematic longitudinal section of a vacuum switch showingthe contacts in an enclosure;

FIG. 2 is an enlarged schematic perspective view of a pair of opposed,axially aligned contacts each having a ring-shaped bridge means thereon;

FIG. 3 is a plan view of the lower contact of FIG. 2 furtherillustrating the chordal alignment of the second portion of the slotmeans and the positioning of the bridging members; and

FIG. 4 is an enlarged cross sectional elevational view taken through thearea indicated by the circled portion IV in FIG. 3.

DESCRIPTION OF A PREFERRED EMBODIMENT Referring to FIG. 11 there may beseen in cross section a vacuum tight enclosure made of acylindricallyshaped insulator member 1 having upper and lower metallicend plates 2 and 3 respectively, which enclosure may be subjected to avery high vacuum. The insulator 11 may be made of a glass or ceremicmaterial. In the housing two switching contacts 4 and 5 generallyaxially aligned and of generally similar size and shape are arranged inpairs opposite and facing toward each other. As shown, the upper contact4 is attached to a generally fixed conductor 6 and the lower contact 5is attached to a movable conductor 7. Each of the condu'ctors 6 and 7are attached to a'suitable electrical potential outside the enclosure. Ametal connector member 8 which may be a metal bellows, seals the vacuumswitch where the conductor 7 is guided movably through the vacuum tighthousing of the vacuum switch.

The contacts 4 and 5 are shown in greater detail in FIGS. 2 through 4.Thus, FIG. 2 is an enlarged perspective view of the contacts andconductors 4, 6 and 5, 7, greatly spaced from each other to allow theconstruction to be clearly seen. As shown, the contacts are nearly fullsize. From FIG. 2 it may be seen that the contacts 4 and 5 may bereferred to as being cupshaped with a ring-shaped bridge means 11upstanding from a generally planar base 9. Since the contacts 4 and 5are the same, the same reference numerals have been used with referenceto each. One side of the base has the ring-shaped bridge means extendingtherefrom, the other side of the base 9 has the conductors 6 and 7,respectively connected thereto. The ringshaped bridge 10 has an upperplanar surface 10a which faces and is generally parallel to the upperplanar surface 10a on the opposing contact. As shown, the contacts 4 and5 are each circular and of similar size. Also, the contact surfaces 10aare of similar width.

The ring-shaped bridge 10 of each of the switching contacts 4 and 5 issubdivided into three segments by slot means having a first portion 11and a second portion 12. The second portion 12 of the slot means is agenerally vertical cut into the ring-shaped bridge 10 extending from theupper contact surface 10a to a point generally even with the ,uppersurface of the base 9. The first portion 11 of the slot means extends inone direction from the second portion 12 of the slot means and lies in aplane parallel to the plane of the contact surface 10a. As shown, thesetwo planes will be generally perpendicular to the central axis of thecontacts and their respective conductors. As may be best seen from F IG.2 the arrangement of the slot means in the contacts 4 and 5 may beidentical so that when the contacts 4 and 5 are positioned in opposite,facing relationship the first portions 11 of the slots will extend inopposite directions from the vertical second portions 12. The contactpieces are advantageously designed symmetrically and arranged in thevacuum switch staggered circumferentially in relationship to each otherby about one-half the length of the segments whereby the current iscaused to flow circumferentially. Thus, the current is forced into apath from its respective conductor through the base 9 into the bridge 10through the portion which connects the bridge 10 with the base and thenpractically exclusively in the circumferential direction of thering-shaped bridges 10 in the segments of the bridges which are abovethe first portion 11 of the slot means. By this means the current islooped about in the rotary path of the segments and in a path parallelto the contact surfaces 10a. These current loops can produce a strongmagnetic field which field is practically exclusively directed verticalto the current direction of a light arc coming about between theswitching contacts 4 and 5 when the contacts are separated. Due to thismagnetic field the light are is moved with extremely high speed over thecontact surface 10a of the ring-shaped bridges 10 in a circular path. Inorder, to assure that the light arc may move freely 4 around thering-shaped bridges the second portions 12 of the slot means arearranged to lie on a chord with respect to the circumference of thering-shaped bridges 10.

The contact arrangement which has been illustrated and described isadvantageously effected in such a way that some of the cross sectionalsurface areas of the current supply with respect to the segments of theringshaped bridge 10, i.e., the'cross sectional surfaces of the bridge10 between a slot 11 and a cut 12 of an ad jacent slot, is equal to thecross section of the rod-shaped conductors 6 or 7, respectively. Theindividual segments 10 are advantageously spaced in the axial directionof the switching pieces 4 and 5 by means of supports 13 in order tomechanically support the individual segments 10 at the end remote fromtheir end of attachment to the base 9. These supports are made of amaterial such as a metal alloy of lower electrical conductivity than thematerial of which the contacts 4 and 5 are formed.

As may be best seen in the cross sectional view of FIG. 4 the supports13 may comprise screws which are inserted through the base 9 of aswitching contact in the area of the free end of the segment of thebridge 10. If the switching contacts 4 and 5 consist mainly of copper,the screw bridging member may consist of an ironnickel-cobalt alloywithout interfering with the current path in the switching contacts.

The invention herein is not limited to the sample embodiment asillustrated. For example, the number of segments does not need to bethree but may be more or less. With respect to the bridging member 13 itwill be understood that this may comprise a ceramic disc rather than theadjustable screw as shown. A vacuum switch according to this inventionis characterized in that high currents such as currents above 4kA can beswitched off safely and reliably by means of this easily andeconomically constructed apparatus. Also, as has been explained indetail, the light arc is necessarily moved extremely fast by themagnetic field over the contact surface 10a whereby the surface 10a willwear very well and as a result the vacuum switch according to theinvention will enjoy a long useful life with little maintenance.

Although minor modifications might be suggested by those versed in theart, it should be understood that I wish to embody within the scope ofthe patent warranted hereon all such modifications as might reasonablyand properly come within the scope of my contribution to the art.

I claim:

1. A vacuum switch means comprising a pair of generally axially alignedopposed disc-shaped contact members with raised portions on the outerperiphery thereof which form a ringshaped bridge means, said bridgemeans having a single generally planar contact surface subdivided intosegments by generally circumferentially extending slot means, said slotmeans having first and second portions, said first portion of said slotmeans lying in a-plane generally parallel to the contact surfaces of thecontacts, whereby current flowing through the bridge means is forcedinto a path with a component extending in the circumferential directionof said ring-shaped bridge means so that a magnetic field is created ina generally axial direction, wherein said second portion of said slotmeans extends between said contact surfaces and said first portion ofsaid slot means, and wherein both of saidv contacts have said ringshapedbridge means thereon, said first portions of said slot means on each ofsaid contacts extending in opposite directions from their respectivesecond portions, and wherein said slot means on one of said contacts iscircumferentially staggered with respect to the slot means on the otherof said contacts, and wherein said slot means are staggered by aboutonehalf the length of said segments.

2. A vacuum switch means according to claim 1 wherein said secondportion of said slot means lies on a chord of the ring-shaped bridgemeans.

3. A vacuum switch means according to claim 1 t 6 wherein saidring-shaped bridge means are each divided into three segments.

4. A vacuum switch means according to claim 1 wherein said firstportions of said slots adjacent said second portions are supported bybridging members consisting of a material which has a lower electricconductivity than the material of the contacts.

5. A vacuum switch means according to claim 4 wherein said bridgingmembers comprise a screw means adjustable to maintain said slot means ata predetermined width.

1. A vacuum switch means comprising a pair of generally axially alignedopposed disc-shaped contact members with raised portions on the outerperiphery thereof which form a ringshaped bridge means, said bridgemeans having a single generally planar contact surface subdivided intosegments by generally circumferentially extending slot means, said slotmeans having first and second portions, said first portion of said slotmeans lying in a plane generally parallel to the contact surfaces of thecontacts, whereby current flowing through the bridge means is forcedinto a path with a component extending in the circumferential directionof said ring-shaped bridge means so that a magnetic field is created ina generally axial direction, wherein said second portion of said slotmeans extends between said contact surfaces and said first portion ofsaid slot means, and wherein both of said contacts have said ringshapedbridge means thereon, said first portions of said slot means on each ofsaid contacts extending in opposite directions from their respectivesecond portions, and wherein said slot means on one of said contacts iscircumferentially staggered with respect to the slot means on the otherof said contacts, and wherein said slot means are staggered by aboutone-half the length of said segments.
 2. A vacuum switch means accordingto claim 1 wherein said second portion of said slot means lies on achord of the ring-shaped bridge means.
 3. A vacuum switch meansaccording to claim 1 wherein said ring-shaped bridge means are eachdivided into three segments.
 4. A vacuum switch means according to claim1 wherein said first portions of said slots adjacent said secondportions are supported by bridging members consisting of a materialwhich has a lower electric conductivity than the material of thecontacts.
 5. A vacuum switch means according to claim 4 wherein saidbridging members comprise a screw means adjustable to maintain said slotmeans at a predetermined width.